A holiday test is an inspection method used to detect discontinuities in painted/coated surfaces using specialized tools and equipment. These tools, called holiday detectors, are portable devices that are swept across the coated surface.

Holidays tests work on the concept of electrical conductivity. Metal substrates are excellent conductors of electricity, and therefore allow current to flow through them. On the other hand, many coatings are poor conductors of electricity and resist the flow of electricity. Using this principle, holiday tests use instruments to locate flaws in anticorrosive paints and coatings.

During holiday testing, a ground wire and probing electrode are attached to the same power source. The ground wire is clamped to the specimen being tested while the probe is swept across the surface of the metal substrate. If the probe comes into contact with a coating discontinuity, the exposed metal completes the electrical circuit between the electrode and the grounding wire, resulting in a flow of electricity. This electricity shows up on an indicator, alerting the equipment operator of the defect.

Premature corrosion of a substrate is usually due to a coating failure. A major cause is the presence of flaws in the finished coating, collectively referred to as porosity. Holiday test is used to detect holes, known as holidays or discontinuities, in a coating. Holiday testing allows the detection of even smallest coating flaws invisible to the naked eye. There are various techniques and equipment available for holiday detection.

Elcometer offers a range of holiday detectors that make holiday detection safer, faster and more reliable than ever before. Elcometer’s range of holiday detection testers uses variety of techniques including high voltage holiday detection and DC pulsed holiday detection. All holiday detectors are available with a wide range of accessories that will allow holiday testing on all types of substrates and applications.